Bernie Sanders slammed Donald Trump’s attack on Bill Clinton, saying the Republican front-runner should concentrate on more important matters.

Trump had earlier raised questions about Bill Clinton’s history of “women abuse,” after his wife and Democratic presidential hopeful Hillary Clinton had said during an interview that Trump “had a penchant for sexism.” Trump’s statement had come on the heels of Hillary Clinton’s announcement that former president Bill Clinton was set to hit the campaign trail on behalf of his wife in January.

Donald Trump had recently also alleged that Hillary Clinton was repeatedly trying to “play the woman card,” remarking that he was the “only one that was willing to talk about [Bill Clinton’s] problems.”

Donald Trump had earlier suggested that attacking Hillary Clinton for Bill Clinton's history with women was "fair-game." (Photo by Spencer Platt/Getty Images)

“We have enormous problems facing this country and I think we got more things to worry about than Bill Clinton’s sexual life. I think — interestingly enough, maybe Donald Trump might want to focus attention on climate change, understand that climate change is not a hoax, as he believes that it is, that maybe Donald Trump should understand that we should raise the minimum wage in this country, which he opposes, and maybe we should not be giving huge tax breaks to fellow billionaires like Donald Trump. So I think maybe he should focus on those things.”

Sanders also called Trump a “pathological liar” for having suggested that he had witnessed thousands of Muslims in New Jersey celebrating the Sept. 11 attacks as the World Trade Center was coming down.

“Time after time, this guy just comes up with things off the top of his head that are lies. And somebody has got to say that he is a pathological liar.”

During the interview, Sanders also backed President Obama on his proposed executive action on guns, despite his own past support for Second Amendment rights as a senator from a largely rural state, according to USA Today.

“I think the American people have been horrified by the mass shootings we’ve seen over the last couple of years. What I think we need to do, among many other things, is do away with the so-called gun show loophole where people are — do not have to go through the instant background check. There is a wide consensus, overwhelming majority of the American people believe we should expand and strengthen the instant background check to keep guns out of the hands of criminals and people with mental health issues. I think that’s what the president is trying to do, and I think that will be the right thing to do.”

A man wearing a Donald Trump T-shirt tried to heckle Bernie Sanders at a campaign stop on Saturday in Amherst, Massachusetts. (YouTube)

In related news, Raw Story reports that Bernie Sanders was heckled at a campaign stop on Saturday in Amherst, Massachusetts by a man wearing a Donald Trump t-shirt, who held a sign which read: “Obama is a Christian… Like Bruce Jenner is a woman.”

Although the heckler was escorted out to continued boos by Sanders’ supporters, the Democratic presidential hopeful pitched in with an attack of his own, remarking, “Here’s a Trump supporter worried about Mr. Trump’s money. I say to Mr. Trump and his supporters that the billionaires in this country will not continue to own this nation.”